Low oil level safety lock and air pocket vent



C. S. TAYLOR Aug. 31, 1965 LOW OIL LEVEL SAFETY LOCK AND AIR POCKET VENT Filed Sept. 27, 1963 2 Sheets-Sheet 1 INVENTOR Can (5 Jay/or 3 6L Z/M'M'n- C. S. TAYLOR Aug. 31, 1965 LOW OIL LEVEL SAFETY LOCK AND AIR POCKET VENT 2 Sheets-Sheet 2 Filed Sept. 27, 1963 INVENTOR. Can J. Jig/0r BY United States Patent 3,203,317 LOW OIL LEVEL SAFETY LOCK AND AIR POCKET VENT Carl S. Taylor, Springfield, Ill., assignor to Dnra Corporation, Oak Park, Mich., a corporation of Michigan Filed Sept. 27, 1963, Ser. No. 312,060 Claims. (Cl. 91'4) This invention relates to semi-hydraulic hoists and lifts in general and more particularly to low oil level safety locks and air pocket vents for use therewith.

Most power operative lifts of the semi-hydraulic type make use of air pressure to displace hydraulic fluid from a chamber area in the plunger or ram into a larger chamber area, in a cylinder within which the ram is disposed, to elevate the ram and a lift frame carried thereon. As will be appreciated, when the fluid level in the ram is lower than necessary to accomplish the desired lift, air under pressure will enter the cylinder area. This causes a momentary loss of power in lifting the ram, because of the compressibility of the air, and then a faltering erratic and uncontrolled movement of the ram under air pressure alone uninhibited by the flow restriction previously provided for the fluid'and which assured a smooth and continuous ascent.

To avoid this problem most manufacturers of semi-hydraulic lifts provide some form of low oil level lock to shut-off the system when the oil level is too low in the ram. This usually includes some form of float provided in the plunger or ram which will seat and shut off the transfer of fluid when the fluid level gets dangerously low and before any serious mishap occurs.

Of necessity, a low oil level lock of the type mentioned must be placed near the lower end of the plunger or ram so that maximum fluid transfer between the ram and cylinder is possible before the fluid is cut-off. As a result, there is a tendency for air which is entrapped in the fluid, and is otherwise in the system and escapes while in the outer cylinder, to collect in an annular pocket between the ram and cylinder walls near the upper end of the cylinder. This area of compressible air is undersirable in the fluid lift system, because of the compressible cushion it provided, and must be vented or exhausted in some way.

The air pocket mentioned has produced many problems and numerous solutions to these problems have been offered. However, most of them have involved rather complicated mechanisms and have been too expensive to be practical.

One of the more practical solutions oflfered to the air pocket problem, particularly with low oil level locks of the type mentioned, is a manual vent tube which opens through a side wall of the plunger, at its upper disposed position, and extends inside and down near the bottom of the plunger past the low oil level mark. However, unless the air pressure in the ram is cut-off when the fluid transfer through the oil lock passage is stopped, fluid is forced through the vent tube and the safety feature of the low oil level lock is completely avoided. If there is a sufficient oil reserve in the ram or plunger, the transfer of fluid through the restricted opening into the vent tube is of no minor consequence. However, once the reserve fluid is exhausted from the ram, and the end of the vent tube is exposed to air pressure in the plunger or ram, the latter will raise without restriction just as it would without the low oil level lock.

It is an object of this invention to provide a vent to exhaust air from air pockets in hydraulic lifts and elsewhere and particularly for use with semi-hydraulic lifts having low oil level safety locks.

It is an object of this invention to provide an air vent for a hydraulic system which will allow the passage of air therethrough in only one direction and only under proper conditions.-

It is an object of this invention to provide a simple inexpensive means of accomplishing the objects aforementioned as well as those which will be better understood and appreciated upon the reading of the following specifications in regard to a preferred embodiment of the invention and having reference to the accompanying drawings wherein:

FIGURE 1 is a coss-sectioned side plan view of a lift shown in a lower disposed position and including the present invention.

FIGURE 2 is a cross-sectional view of the lift shown by FIGURE 1 with the ram disposed in an elevated position.

FIGURE 3 is a fragmentary cross-sectioned view similar to FIGURE 2 with a low oil level condition existing within the ram.

FIGURE 4 is an enlarged cross-sectional view of a fragmentary part of the lift shown by the previous figures and showing certain features in greater detail.

FIGURE 5 is an enlarged cross-sectional view of the vent tube check valve of this invention as seen in the plane of the line 55 of FIGURE 4.

The semi-hydraulic hoist or lift 10 shown in the drawings includes an outer cylinder member 12 having a plunger or ram 14 provided therein and having an air pressure line 16 connected thereto for introducing air into the top of the ram and forcing hydraulic fluid 18 from the ram into the cylinder to cause the elevation of the former.

The outer cylinder member 12 is normally embedded in the ground below the ground level line 20 and includes a cylindrical case 22 having a bottom closure 24. The air pressure line 16 extends through the bottom closure 24 and a packing gland or stufiing box 26 is provided at the top of the cylinder to receive the plunger or ram 14 in relatively sealed and guided relation therethrough.

The plunger or ram member 14 includes a smaller cylindrical body member 28 which is concentrically disposed within the outer cylinder body member 12. It includes a bottom closure 30 having a packing gland 32 through which is received the air pressure line 16. The top of the ram cylinder 28 also includes a closure 34 with a guide rod 36 provided thereon and depending into the air pressure line 16.

A carrier frame 38 is provided on a upper disposed end of the plunger or ram 14 for whatever lift serving purpose is desired.

A fluid passage 40 is provided through the bottom wall 30 of the plunger or ram 14. A perforated tube 42 has one end disposed in the fluid passage 40 and the other end secured to a guide fixture 44 secured to the upper closure wall 34 of the ram cylinder.

A float 46 is provided in the perforated tube 42. AS will later be described, the float 46 is adapted to close the fluid passage 40 when the fluid level in the ram 14 falls below a prescribed level and before an air passage is created between the ram and the outer cylinder.

In the lower disposed position of the ram 14 within the outer cylinder 12, as shown by FIGURE 1, the plunger or ram is essentially filled with the fluid 18. The annular space 48 between the ram and the cylinder is also filled with fluid, the oil lock float 46 is disposed high in the perforated tube 42 and the fluid passage 40 is open between the two cylinders.

If there is any air trapped in the outer cylinder, it will be appreciated that it will come to the top of the annular space 48 between the cylinders and form an air pocket 50 therebetween.

The plunger or ram 14 is raised by the introduction of air through the air pressure supply line 16 into the top of the ram. This forces the fluid 18 through the passage 40 and into the outer cylinder 12. As the fluid level in the ram falls, the float 46 in the perforated tube 42 drops With the level of the fluid.

Under normal circumstances the air pressure supply to the ram will be automatically cut-off when the ram reaches its proper height and this will occur with ample fluid left in the ram. However, if for any reason the oil level is low in the ram before it reaches its full height, the float 46 will seat in the fluid passage 40 and stop the transfer of fluid and consequently the elevation of the ram.

Approaching now the problem of venting the air pocket 50:

In elevating the ram 14, the fluid in the ram is und r greater pressure than in the cylinder; as necessary to affect the flow of fluid from the ram to the cylinder. When the ram is fully elevated and the air pressure is cut-off, then the fluid pressure becomes equal in the ram and the outer cylinder. When the air pressure is released in the ram, n the fluid pressure is greater in the cylinder and fluid is forced through the restricted passage 40 back into the ram.

It follows from the foregoing that the best time to vent the air pocket 50 is either when the ram is at its upper disposed position, and the air pressure is cut-off, or during its descent. The initial part of the descent stroke will be subsequently appreciated as when the venting actually occurs in this embodiment of the invention.

Referring to FIGURE 3:

A vent tube 52 is shown vertically disposed within the ram 14- and having its upper disposed end 54 extended through an opening 56 in the side wall of the ram and welded thereto. The open end of the vent tube 52 extends through the ram wall and is disposed for alignment with the air pocket 50 when the ram is at its fully raised position. The lower end 58 of the vent tube is extended in spaced relation to the lower end or bottom of the ram and below the low oil level mark determined by the seating of the float 46 in the fluid passage 40.

The vent tube, as described, will pass fluid ther-ethrough in the course of raising the ram since the fluid pressure is greater in the ram than in the cylinder. However, this is of no great consequence during the elevation of the ram since fluid is being passed through the passage 40 anyway. At the same time, when the ram is in its upwardly disposed position and begins its descent, and pressure is greater in the cylinder, then air will be vented from the air pocket 59. Although there will be some fluid transferred through the vent tube during the descent of the ram this, again, is of no consequence.

As long as the fluid level in the ram does not fall below the lower disposed end 58 of the vent tube before the air pressure is cut-off in the ram, the unobstructed openended vent tube serves perfectly well. However, if the air pressure in the ram is not cut-off before the low level reserve is forced by this air pressure through the vent tube then an open passage is create-d through to the outer cylinder and the safety of the low oil level lock float 46 is completely avoided.

Referring now to FIGURES 4 and in particular:

To safeguard the hydraulic system against by-passing the low oil level lock provided by the float 46, and still be able to vent the air pocket 50, a check valve device 60 is provided at the lower end of the vent tube 52.

The check valve device 66 includes a steel ball member 62 which is provided within a larger bore 64 preformed within the end of the vent tube and a ball check seat 66 which is provided thereon and further in the vent tube. A cotter pin 68 is extended laterally through the vent tube sufliciently below the ball check 66 so that the weighted ball 62 is normally disposed off the valve seat 66.

When the ram 14 is being elevated, and the fluid pressure in the ram is greatest, the ball 62 is held against float 46 seats in the fluid passage 40, and there is still air pressure in the ram, the fluid pressure on the ball 62 keeps it seated and no fluid escapes through the vent tube.

When the air pressure is cut-off in the ram, or the fluid pressure is greater in the cylinder, the weighted ball 62 falls back from the seat 66 and against the cotter pin stop 68. This enables the fluid within the ram and cylinder to seek its own level and, during the descent of the ram, when pressure is greater in the cylinder, for the air to be forced out of the pocket Sit.

Although there may be some fluid transfer from the cylinder to the ram during the descent of the ram, this is of no consequence, as previously mentioned.

From the foregoing it will be appreciated that the very simple innovation disclosed, and which may be made at a nominal expense and yet in the absence of this disclosure was not obvious, has solved a very dangerous situation in a most ingenious way.

Although a very specific embodiment of this invention has been shown and described, it will be appreciated that certain modifications and improvements are within the scope of the teachings set forth. Accordingly, such improvements and modifications as are within the spirit of this invention and are not specifically excluded by the language of the hereinafter appended claims are to be considered as inclusive thereunder.

I claim:

1. An air pocket vent for vertically oriented semihydraulic lifts and the like including an air pressure receptive and fluid exhausting ram disposed within an outer cylinder receptive of the fluid exhausted from said ram for the elevation of said ram relative thereto, and which have an air pocket formed therebetween and in the outer cylinder, and comprising:

vent passage means carried by said ram,

said vent passage means being vertically disposed and open at the upper end thereof externally of said ram and for communication with the air pocket in the outer cylinder,

said vent passage means having the lower disposed end thereof open within said ram near the lower end of said ram and below the low oil level mark therefore,

and check valve means operatively disposed within said vent tube and responsive to greater pressure in said ram than at said air pocket end for closure thereof and a reverse pressure condition for the opening thereof and venting of said air pocket.

2. The air pocket vent of claim 1,

said check valve means being provided at the lower disposed end of said vent tube and below the low oil level mark within said ram.

3. The air pocket vent of claim 1,

said check valve means including a ball check member disposed near the ram end of said passage means and a receptive seat disposed next adjacent thereto and on the air pocket side thereof.

4. The air pocket vent of claim 1,

said check valve means including a weighted ball provided in the lower disposed end of said vent passage means and a receptive seat provided in said passage means next adjacent thereto and thereover.

5. An air pocket vent for vertically oriented semihydraulic lifts and the like including an air pressure receptive and fluid exhausting ram disposed within an outer cylinder receptive of the fluid exhausted from said ram for the elevation of said ram relative thereto, and which have an air pocket formed therebetween and in the outer cylinder and comprising:

a vent tube disposed in said ram and having one end thereof extend through the side wall thereof for open communication with the air pocket of the outer cylinder externally thereof,

said vent tube being vertically disposed and having the other end thereof open in said ram below the air pocket end thereof and below the low oil level mark within said ram,

3,203,317 5 6 an enlarged bore provided in the lower open end of References Cited by the Examiner said vent tube and formed to include a ball seat at the air Pocket end thereof UNITED STATES PATENTS a Weighted ball provided in said bore for engagement 2,254,699 9/41 Jaseph 91-4 with said ball seat and closure of said vent tube 5 2,550,882 5/51 Strum 91-4 under fluid pressure from within said ram, 2,588,285 3 5 p l and means provided across the open lower end of said 3,112,676 12/63 Boulsorer vent tube and spaced from said ball seat for retaining said weighted ball in said tube and spaced from said FRED ENGELTHALER primary seat for air venting and fluid passage through said 10 tube on the relief of pressure within said ram. 

1. AN AIR POCKET VENT FOR VERTICALLY ORIENTED SEMIHYDRAULIC LIFTS AND THE LIKE INCLUDING AN AIR PRESSURE RECEPTIVE AND FLUID EXHAUSTING RAM DISPOSED WITHIN AN OUTER CYLINDER RECEPTIVE OF THE FLUID EXHAUSTED FROM SAID RAM FOR THE ELEVATION OF SAID RAM RELATIVE THERETO, AND WHICH HAVE AN AIR POCKET FORMED THEREBETWEEN AND IN THE OUTER CYLINDER, AND COMPRISING: VENT PASSAGE MEANS CARRIED BY SAID RAM, SAID VENT PASSAGE MEANS BEING VERTICALLY DISPOSED AND OPEN AT THE UPPER END THEREOF EXTERNALLY OF SAID RAM AND FOR COMMUNICATION WITH THE AIR POCKET IN THE OUTER CYLINDER, SAID VENT PASSAGE MEANS HAVING THE LOWER DISPOSED END THEREOF OPEN WITHIN SAID RAM NEAR THE LOWER END OF SAID RAM AND BELOW THE LOW OIL LEVEL MARK THEREFORE, AND CHECK VALVE MEANS OPERATIVELY DISPOSED WITHIN SAID VENT TUBE AND RESPONSIVE TO GREATER PRESSURE IN SAID RAM THAN AT SAID AIR POCKET END FOR CLOSURE THEREOF AND A REVERSE PRESSURE CONDITION FOR THE OPENING THEREOF AND VENTING OF SAID AIR POCKET. 